Biobarcode

Hill HD, Mirkin CA. The biobarcode assay for the detection of protein and nucleic acid targets using DTT-induced hgand exchange. Nat. Rotoc. 2006 1 324-336. 

Figure 12.12 Biobarcode assay for DNA detection. Magnetic microparticles (Mag) hybridize to specific targets. AuNPs functionalized with target-specific barcode strands are then added. After magnetic separation, the barcodes are released from the surface of the AuNPs by DTT. Subsequently the barcodes are detected using the scanometric method. (Reproduced with permission fi om C. S. Thaxton et al., Anal. Chem. 2005, 77, 8174-8178. Copyright 2005 American Chemical Society.) (See color insert.)...

Q13 nm Au nanoparticles IgGI (Anti-biotin) IgE (Anti-DNP) nmnmi. Biobarcode DNA... 

While this prototype assay was relatively simple, the LOD was only 20 nM, still far above that of a conventional ELISA method. To overcome the hmitations of the prototype protein assay, a new generation of the biobarcode assay for protein detection was developed (66). The fundamental scheme of this assay is similar to the biobarcode assay for DNA detection discussed previously. This assay relies on MMPs functionalized with antibodies specific to the target protein. To enable protein detection and take... 

In addition to the solution-phase protein detection assays such as biobarcode assays, a surface-based protein detection method was developed by Niemeyer and Ceyhan (70). In this work, a biotin-labeled antibody was conjugated to DNA using streptavidin as a tinker molecule. This conjugate was hybridized to complementary DNA-AuNPs and antibody-functionalized AuNPs. These particles are allowed to form a sandwich structure with a target protein and a second antibody immobilized on a flat surface. This was followed by a silver enhancement step catalyzed by the AuNPs which resulted in a LOD of 50 fmol (200 pM). This method is conceptually similar to the corresponding surface-based scanometric detection of DNA. Further work demonstrated a similar protein detection scheme without the silver enhancement (71). Instead, multiple layers of secondary DNA-AuNPs were used to increase signal enhancement [LOD = 0.1 finol (2 pM)]. 

C) Biobarcode assay and scanometric detection of Itie barcodes... 

Keywords— Localized surface plasmon resonance, particle aggregation, catalytic property, fluorescence resonance enei transfer, biobarcode. 

The advent of biobarcode technology [24—26] may help to improve medical diagnostics. Nanobarcodes are metallic barcodes with unique patterns prepared by the sequential electrochemical deposition of metal ions. The different reflectivity of the individual metallic barcodes enables identification of analyte. This method has shown promise for detecting protein analytes where the technology relies on magnetic nanoprobes with antibodies that specifically bind a target of interest [27]. 

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